We know they're there. In the Stars arc, Seiya said that any planet, regardless of size, that had life, also had a Senshi. I interpret this to mean anything big enough to possibly hold a kingdom, so that excludes microscopic asteroids but includes larger ones. The ones large enough to have names are probably large enough for kingdoms, at least that's what I'm going on. This 기사 will list all of the named asteroids/minor planets and dwarf planets and what I think Senshi from each would be like.

Edit: OK, there could probably be 100 더 많이 Senshi for every named asteroid. I'm just going to stop...